A rotational stitching method for measuring cylindrical surfaces

It is difficult for traditional measurement instruments such as white light interferometers and coordinate measuring machines to measure cylindrical surfaces such as grinding wheels since most of these instruments only have 2.5D measurement capability so that the data may be missing in the bottom section of the workpieces. Moreover, the area near the edge where the surface gradient is high would be susceptible to large measurement uncertainty for some instruments. To address these shortcomings, this paper presents a method named Rotational Stitching Method (RSM) which attempts to measure the whole cylindrical surface. The method is used to measure a grinding wheel mounted on the shaft of a step motor which can be controlled and rotated with pre-set micro steps. A series of measurement experiments are designed to measure the top surfaces of the grinding wheel with a white light interferometer for every certain angle and the measurements are designed to have overlapped regions for registration. After the sub-measurements cover the whole cylindrical surface, the measurement datasets of the sub-surfaces are stitched and fused together to form the holistic surface of the grinding wheel. The motion errors of the grinding wheel including the rotation error of the motor, and alignment error can be eliminated or minimized by the stitching process. The capability of the method is realized by measurement experiments.